Abstract Many, but not all, fishes use accessory hearts as auxillary venous pumps to help blood both from within the venous system and from the secondary circulation return toward the branchial heart. One type of accessory heart, the myogenic portal heart of hagfishes, is unique, because it is the only example of cardiac muscle lying outside of the pericardium. Its heartbeat helps pump venous blood from the gut to the liver. The other accessory pumps are variably designed around a theme of valved chambers that are compressed by skeletal muscle, sometimes against skeletal elements. Examples are found in fishes as diverse as hagfishes, sharks, and eels.